The present invention generally relates to a semiconductor wafer test or transfer machine. More particularly, the invention relates to rapid cooling of a wafer test/transfer machine in the testing and transferring of semiconductor wafers during semiconductor production.
A conventional method used by the semiconductor industry in the manufacturing of semiconductor integrated circuits includes the steps of fabrication, wafer sort, assembly and test, respectively. In the fabrication step, as many as several thousand dies (integrated circuits) are formed onto a semiconductor wafer. In the wafer sort step, each of the dies on the wafer is tested to determine its electrical characteristics and operability, and defective dies are distinguished from operable dies. The defective dies are often marked by an ink mark at the wafer sorting step. In the assembly step, the unmarked, operable dies are assembled into a package, and in the test step, the packaged integrated circuits are tested for operability and reliability.
Each of the fabrication, wafer sort, assembly and test steps may be further broken down into smaller steps carried out at multiple stations. These may include one or more measurement stations for receiving wafers and measuring or testing various wafer parameters, as well as packaging and shipping stations. Because excessive human handling and transport of the wafers between stations increases the possibility of contamination and inadvertent damage to the wafers, the wafers are typically transferred from one station to another using a wafer test/transfer machine or wafer prober. The various electrical characteristics of the wafers are also tested on the wafer prober, which holds the wafers at a stationary position where the testing or other process is performed.
In a typical wafer prober, a semiconductor wafer is mounted on the top surface of a wafer chuck inside the prober. A vacuum system is connected to the wafer chuck, and a series of concentric vacuum grooves in the top surface of the chuck conduct the vacuum to the wafer to secure the wafer in place on the chuck. The prober includes a group of electrical probes on a probe card which apply predetermined electrical currents to various predetermined portions of the die on the wafers, and a tester senses the dies"" responses to the currents.
The wafer sort and test steps for semiconductor wafers may also include heat-screening of the wafers. Accordingly, the wafer prober is provided with a heater for heating the chuck and the semiconductor wafer held thereon. Before the heat-testing of the semiconductor wafer in the wafer probe, the chuck must be at a relatively cool temperature as the wafer is loaded on the chuck to prevent sudden heating of the wafer and thermal shock damage thereto. Furthermore, the wafer probe may be used to transfer the wafer from one station to another at room temperature. One of the problems realized in the operation and use of conventional wafer probers is that a long period of time is required for the chuck of the wafer prober to cool down to a sufficient temperature to enable safe loading of the semiconductor wafer onto the chuck for subsequent heat-testing of the wafer or for transfer of the wafer between stations at room temperature.
Therefore, it is an object of the present invention to facilitate rapid cooling of a chuck or other wafer holder on a semiconductor wafer prober or wafer test/transfer machine.
It is another object of the present invention to substantially decrease the time ordinarily required for cooling of a wafer holder in a semiconductor wafer test/transfer machine.
It is yet another object of the present invention to enhance efficiency in the production of semiconductor integrated circuits by increasing the batch volume of semiconductor wafers capable of being tested and transferred over a given period of time in a semiconductor production facility.
It is still another object of the present invention to facilitate rapid cooling of a wafer chuck or other wafer holder in a semiconductor wafer transfer/test machine by utilizing compressed air or other gas to dissipate heat.
It is a further object of the present invention to provide a device which can be held by hand for rapidly cooling a wafer holder in a semiconductor wafer test/transfer machine.
In accordance with these and other objects and advantages, the present invention comprises a body which is provided with an interior gas passage one end of which is connected to a source of clean, dry air or other gas by a tubing. The body is rested on the cover of a semiconductor wafer test or transfer machine, typically above or adjacent to the chuck or other wafer holder of the machine, with the other end of the gas passage in contact with the cover. The clean, dry air or other gas flowing under pressure through the gas passage impinges against the machine cover and rapidly cools the chuck or other wafer holder.